What payroll taxes are and why they come out of your check

Payroll taxes are amounts your employer withholds from your paycheck and sends to federal and state governments. They fund Social Security, Medicare, unemployment insurance, and income tax. Your employer also pays a matching amount on your behalf — you do not see this, but it exists. The taxes that come out of your check are not optional; federal law requires them.

The amount withheld depends on three things: your gross pay (what you earn before deductions), your filing status (single, married, head of household), and the number of dependents you claim. You control the last two by filling out a W-4 form when you start a job. The calculation itself is mechanical — your employer's payroll system does it automatically using IRS tables.

Key Takeaways

  • Federal income tax withholding is based on your W-4 form, which tells your employer how much to deduct based on your filing status and dependents.
  • Social Security tax is 6.2 percent of your gross pay, up to a yearly cap that changes each year; Medicare tax is 1.45 percent with no cap.
  • State and local income taxes vary by where you live and work; some states have no income tax at all.
  • You can change your withholding mid-year by submitting a new W-4 to your employer if your life situation changes.
  • The IRS provides a withholding calculator on its website to help you estimate whether you are having too much or too little withheld.

Federal income tax withholding and the W-4 form

Federal income tax withholding starts with the W-4 form (Employees Withholding Certificate), which you complete when hired. On it, you declare your filing status, number of dependents, and any other income or jobs. Your employer uses this information plus IRS withholding tables to calculate how much federal tax to take from each paycheck.

The IRS publishes new withholding tables each year. Your employer's payroll software applies these tables automatically — you do not calculate it yourself. If you claim zero dependents and are single, more tax comes out. If you claim dependents or are married filing jointly, less comes out. The system assumes you will owe taxes at the end of the year; the withholding is an estimate meant to get you close.

You can change your W-4 at any time by submitting a new form to your employer's payroll department. This is useful if you get married, have a child, take a second job, or realize you are having too much or too little withheld. The change takes effect on your next paycheck.

Social Security and Medicare taxes (FICA)

FICA taxes (Federal Insurance Contributions Act) include Social Security and Medicare. These are fixed percentages of your gross pay, not based on your W-4. Your employer withholds them automatically and matches them dollar-for-dollar.

Social Security tax is 6.2 percent of your gross pay. However, there is a yearly earnings cap — in 2024, you stop paying Social Security tax once you earn $168,600. After that threshold, no more Social Security tax comes out for the rest of the year. This cap changes each year. Medicare tax is 1.45 percent of your gross pay with no cap — you pay it on every dollar you earn, no matter how much.

If you earn over $200,000 (single) or $250,000 (married filing jointly), an additional 0.9 percent Medicare tax applies to income above those thresholds. Your employer withholds this automatically if your pay crosses the threshold. These amounts are set by law and do not change based on your W-4.

State and local income taxes

State income tax withholding varies dramatically by location. Nine states have no state income tax at all: Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, Wyoming, and New Hampshire (which taxes only dividends and interest, not wages). If you live and work in one of these states, no state income tax comes out of your check.

In states that do tax income, the withholding process is similar to federal: you fill out a state W-4 (or equivalent form) when hired, and your employer withholds based on your filing status and dependents. Some states use the same percentages and tables year to year; others adjust them. A few states allow you to claim additional withholding if you expect to owe at tax time.

Local taxes (city or county income tax) exist in some places — notably New York City, Philadelphia, and parts of Ohio and Kentucky. These are separate from state tax and use their own withholding forms. If you work in a locality with income tax, your employer withholds it in addition to state and federal tax.

How to read your pay stub and verify the math

Your pay stub shows gross pay, each deduction, and net pay (take-home). The deductions section lists federal income tax, Social Security, Medicare, state tax, local tax if applicable, and any other deductions like health insurance or retirement contributions.

To verify the math: multiply your gross pay by 0.062 for Social Security (up to the yearly cap) and by 0.0145 for Medicare. These should match the amounts on your stub. Federal income tax is harder to verify without the IRS tables, but you can use the IRS withholding calculator to see if your total withholding for the year is in the right ballpark. If you notice a large discrepancy or a deduction you do not recognize, ask your payroll department to explain it.

What happens if too much or too little is withheld

If too much tax is withheld throughout the year, you receive a refund when you file your tax return. If too little is withheld, you owe money when you file. Neither is ideal — a large refund means you gave the government an interest-free loan, and owing money means you may face penalties if you did not pay enough during the year.

The IRS provides a withholding calculator on its website (irs.gov) that estimates whether your current withholding is on track. You enter your income, filing status, dependents, and other jobs, and it tells you whether to adjust your W-4. If the calculator suggests a change, you submit a new W-4 to your employer, and the adjustment takes effect on your next paycheck.

Common reasons to adjust: getting married or divorced, having a child, taking a second job, or a spouse starting work. Each of these changes the amount of tax you should have withheld. Adjusting mid-year is free and takes five minutes.

Self-employment taxes if you have side income

If you earn money from self-employment (freelance work, a side business, gig work), you owe self-employment tax in addition to income tax. Self-employment tax covers Social Security and Medicare for people who do not have an employer withholding for them.

Self-employment tax is 15.3 percent of your net self-employment income (92.35 percent of gross income minus business expenses). You calculate and pay this yourself, usually quarterly, using Form 1040-ES. Unlike W-2 employees, no one withholds it for you. If you do not pay quarterly, you may owe penalties at tax time.

If you have both W-2 income and self-employment income, the calculation is more complex because the Social Security portion has a yearly cap. A tax professional or tax software can help you figure the exact amount. The IRS website also has worksheets for self-employment tax.

Frequently Asked Questions

Why does my paycheck vary if I work the same hours every week?

Payroll taxes are calculated on gross pay, which may vary if you work overtime, receive bonuses, or take unpaid time off. Overtime is usually taxed at the same rate as regular pay, so a week with overtime has higher gross pay and higher tax withholding. Bonuses are also subject to withholding. If you take unpaid leave, your gross pay drops that week, so taxes drop too.

Can I claim zero dependents to have more tax withheld?

Yes. Claiming zero dependents increases your withholding even if you have dependents. This is useful if you have other income (a side job, investment income) that is not subject to withholding, or if you simply want a larger refund. You control this by submitting a new W-4 to your employer.

What if I work in one state but live in another?

You typically owe income tax to the state where you work, not where you live. However, some states have reciprocal agreements that allow you to pay tax to your home state instead. Your employer withholds based on where you work unless you provide documentation of a reciprocal agreement. Check your state's tax agency website for details.

Do I have to pay taxes on tips?

Yes. Tips are taxable income. If you receive tips, you should report them to your employer, and they will include them in your gross pay for tax withholding purposes. If you do not report tips, you may owe taxes and penalties when you file your return.

What is the difference between withholding and actually owing taxes?

Withholding is money your employer takes out during the year. Owing taxes is what you owe after you file your return and calculate your actual tax liability. If withholding exceeds what you owe, you get a refund. If you owe more than was withheld, you pay the difference when you file.